1. Spack: A Package Manager for
Supercomputers, Linux and MacOS
Massimiliano Culpo
SCITAS - EPFL

2. The complexity of scientific software threatens productivity
Scientific software must be easy to deploy and use.
● Developers, users and facilities spend a lot of time building and porting scientific software
● Not much standardization in HPC: we are prone to trade portability for performance!
● Target machines may be very different from one another
● Applications need to be tested against different dependencies / compilers to ensure portability
lots of combinations to deploy or test!
# of compilers
# of programming models
MPI, LAPACK, BLAS, ...
# of versions of each
package
# of applications # of software packages
# of target architectures
Xeon, Power, Nvidia, KNL, ...

3. What can we do at HPC sites when software is easy to deploy?
To reach these goals, we need more automation.
Provide to developers:
● Multiple options for the same service (OpenMPI,
MVAPICH2, IntelMPI, ...)
● A more extensive choice of compilers
● Easy ways to set-up development environments
Provide to end-users:
● The best tuning of scientific applications
● Convenient ways to use them
And as cluster maintainers:
● We struggle less with installations
● We can explore a broader range of possibilities
before deciding what to install for users
● We can easily reproduce a software stack

4. How do we automate things then?

5. Spack: a package manager for Supercomputers
github.com/LLNL/spack
1. Get Spack:
2. Set it up:
3. Install a package:
$ git clone https://github.com/LLNL/spack
$ . spack/share/spack/setup-env.sh
$ spack install hdf5
Hdf5 and all of its dependencies are downloaded, built and installed within spack
directory

6. What is a package manager?
Spack is a “package manager”:
● Drives build systems, but does not
replace them
● Manages dependency DAGs
● Ensures consistent builds
Packages within Spack:
● Can have any build system they want
● Don’t need sources to be modified in any
way (pristine sources)
Figuring out configure options takes time:
● Spack is a cache of recipes
● The effort is shared across teams
● Manages dependencies
● Drives package-level:
○ build systems
○ binary installs
Package
Manager
● CMake, Autotools
● Handles library abstractions
● Generates Makefile, etc.
High Level
Build System
● Make, Ninja
● Drives build systems
● Drives binary installs
Low Level
Build System

7. What makes Spack different from other similar tools?

8. Spack handles combinatorial software complexity
spack/opt/
linux-x86_64/
gcc-4.7.2/
mpileaks-1.1-0f54bf34cadk/
intel-14.1/
hdf5-1.8.15-lkf14aq3nqiz/
bgq/
xl-12.1/
hdf5-1-8.16-fqb3a15abrwx/
...
Hash
Dependency DAG
Installation Layout
Each graph of dependencies:
● Represents a unique configuration
● Can be mapped to a unique hash
Each configuration:
● Is installed in a unique directory
● The hash of the graph is appended to
the each prefix
Installed packages:
● Have RPATHs embedded in binaries
● No need to set LD_LIBRARY_PATH or
similar for Spack built packages
● Things work the way they were built

9. Spack can retrieve the full configuration of installed packages
$ spack find callpath
==> 2 installed packages.
-- linux-x86_64 / clang@3.4 ---- -- linux-x86_64 / gcc@4.9.2 -------------
callpath@1.0.2 callpath@1.0.2
$ spack find -dl callpath
==> 2 installed packages.
-- linux-x86_64 / clang@3.4 ----------- -- linux-x86_64 / gcc@4.9.2 -----------
xv2clz2 callpath@1.0.2 udltshs callpath@1.0.2
ckjazss ^adept-utils@1.0.1 rfsu7fb ^adept-utils@1.0.1
3ws43m4 ^boost@1.59.0 ybet64y ^boost@1.55.0
ft7znm6 ^mpich@3.1.4 aa4ar6i ^mpich@3.1.4
qqnuet3 ^dyninst@8.2.1 tmnnge5 ^dyninst@8.2.1
3ws43m4 ^boost@1.59.0 ybet64y ^boost@1.55.0
g65rdud ^libdwarf@20130729 g2mxrl2 ^libdwarf@20130729
cj5p5fk ^libelf@0.8.13 ynpai3j ^libelf@0.8.13
cj5p5fk ^libelf@0.8.13 ynpai3j ^libelf@0.8.13
g65rdud ^libdwarf@20130729 g2mxrl2 ^libdwarf@20130729
cj5p5fk ^libelf@0.8.13 ynpai3j ^libelf@0.8.13
cj5p5fk ^libelf@0.8.13 ynpai3j ^libelf@0.8.13
ft7znm6 ^mpich@3.1.4 aa4ar6i ^mpich@3.1.4
Spack stores the information on installed packages in a DB, and can query it at any
time

10. Spack provides a spec syntax to describe DAG configurations
$ spack install mpileaks
$ spack install mpileaks@3.3
$ spack install mpileaks@3.3 %gcc@5.3.0
$ spack install mpileaks@3.3 %gcc@5.3.0 +threads
$ spack install mpileaks@3.3 cppflags=”-O3”
$ spack install mpileaks@3.3 target=haswell
$ spack install mpileaks@3.3 ^mpich@3.2 %gcc@5.3.0
Each expression is a spec for a particular configuration:
● Clauses represent constraints to the spec
● Constraints are optional, and you can specify only what you really need
● Installations can be customized on the command line
Spec syntax is recursive and gives full control over the combinatorial build space

11. Spack can constrain versions and options of dependencies
$ spack install mpileaks %intel@12.1 ^libelf@0.8.12
Spack ensures one configuration of each library per DAG
● Ensures ABI consistency
● Users do not need to know the DAG structure, only the dependency names
● Builds use the same compiler by default, but you can mix them
Spack handles ABI-incompatible, versioned interfaces like MPI
$ spack install mpileaks ^mvapich@1.9 $ spack install mpileaks ^mpi@2
Spack permits you to specify an implementation of a virtual dependency, or just the
version of its interface

12. Spack fills in the details when the user is not explicit
mpileaks
callpath@1.0
+debug
mpileaks ^callpath@1.0 +debug ^libelf@0.8.11
dyninstmpi
libdwarf
libelf@0.8.11
Normalize
mpileaks@2.3
%gcc@4.7.3
=linux-ppc64
callpath@1.0
%gcc@4.7.3+debug
=linux-ppc64
dyninst@8.1.2
%gcc@4.7.3
=linux-ppc64
mpich@3.0.4
%gcc@4.7.3
=linux-ppc64
libdwarf@20130729
%gcc@4.7.3
=linux-ppc64
libelf@0.8.11
%gcc@4.7.3
=linux-ppc64
Concretize
The user inputs an abstract spec with some constraints, Spack fully constrains it and
passes the concrete configuration to install

13. Spack builds each package in its own compilation environment
do_install()
Install dep 1 Install dep 2 ...
Spack
process
Set up environment
CC = spack/env/gcc
SPACK_CC = /usr/bin/gcc
CXX = spack/env/g++
...
PKG_CONFIG_PATH = …
CMAKE_PREFIX_PATH = …
PATH = ...
Build
process
Fork
install() configure make make install
gcc
Compiler wrappers
● Add include and libs search paths
● Add RPATH flags
● Ensure dependencies are found
● Load Cray modules
● Injects compiler flags on demand
g++ gfortran
Forked build process isolates the environment
for each build.
Compiler wrappers hide part of the complexity.

14. Spack packages are simple Python scripts
Metadata
Versions
and URLs
Patches, variants
(not shown)
Dependencies
Commands for
installation

15. Spack integrates well into different workflows
Spack generates module files or local views to ease the use of installed software.
$ spack module refresh -m tcl

16. Spack integrates well into different workflows
Spack generates module files or local views to ease the use of installed software.
$ spack view symlink <path> <spec>
${HOME}/local_view/
├── bin
...
└── x86_64-pc-linux-gnu-gfortran -> .../gcc-4.8/gcc-6.3.0-mkau7f7p/bin/x86_64-pc-linux-gnu-gfortran
├── doc
├── include
├── ansidecl.h -> spack/opt/spack/linux-ubuntu14-x86_64/gcc-4.8/binutils-2.27-l7va7nysnq/include/ansidecl.h
...
├── boost
└── zlib.h -> spack/opt/spack/linux-ubuntu14-x86_64/gcc-6.3.0/zlib-1.2.10-riqxnllm4s/include/zlib.h
├── lib
├── engines
...
├── libz.so.1.2.10 -> spack/opt/spack/linux-ubuntu14-x86_64/gcc-6.3.0/zlib-1.2.10-riqxnllm4s/lib/libz.so.1.2.10
└── pkgconfig
├── lib64
├── libexec
├── man
├── share
└── x86_64-pc-linux-gnu

17. How can people contribute?

18. Spack is sustained by its community
Spack is hosted on Github:
● LLNL people are extremely open to new
contributions
● More than 30 organizations, more than
100 contributors
Spack is already used in production:
● LLNL, ANL, EPFL
● ...
Github permits to manage contributions:
● Gitflow-like development
● Continuous integration, code coverage
● Fork and pull-requests
● Code-reviews, discussions on features

19. Contributions to Spack have grown rapidly after SC15

20. Spack is well documented
Readthedocs:
● Generate docs using Sphinx
● Keeps docs in sync
● Old versions are kept

21. Questions?